Troyer syndrome is a "complex" form of an autosomal recessive hereditary spastic paraplegia that results from a frameshift mutation in the spartin gene, SPG20. The syndrome manifests in early childhood, and affected individuals exhibit spasticity of the lower limbs, mental retardation and short stature. The lack of basic knowledge of the cellular role of spartin is a critical impediment to understanding the molecular pathogenesis of Troyer syndrome. The proposed studies will examine the physiological function(s) of spartin and its localization in non-neuronal and neuronal cells. We have generated an antibody that specifically recognizes the spartin protein, and our preliminary studies using yeast-two hybrid screening have identified spartin-binding partners whose roles in intracellular trafficking and specific signal transduction pathway are well characterized. On the basis of those empirical studies, we propose the following Aims: 1) Identify the post-translational modifications of spartin and its ultrastructural localization in cells;2) examine the interactions of spartin with its binding partners by using immunoprecipitation and FRET analysis in cultured cells treated with relevant factors that triggers the cascade of cellular events during which the particular interactions may occur;3) generate and express spartin deletion constructs and use them and siRNA to test their effects on intracellular molecular trafficking and signal transduction pathways and 4) make a targeting construct to delete the murine spg20 gene for future studies to generate spartin knock-out mice. Our studies will not only provide detailed characterization of the functional roles of spartin at the cellular level, but will also extend our knowledge of the basic biological processes underpinning the molecular trafficking in the cell. These studies, mentored by Dr. Craig Blackstone, will provide the candidate with training in protein biochemistry and cutting edge techniques to analyze protein functions. The mentored guidance along with the highly interactive research environment at the NINDS ensures the accomplishment of the proposed objectives while allowing the candidate to develop an independent research program.